US2592501A

US2592501A - Hydraulic scale capsule

Info

Publication number: US2592501A
Application number: US126531A
Authority: US
Inventors: Lawrence S Williams
Original assignee: Toledo Scale Corp
Current assignee: Toledo Scale Corp
Priority date: 1949-11-10
Filing date: 1949-11-10
Publication date: 1952-04-08
Anticipated expiration: 1969-04-08

Description

April 8, 1952 1 s. WILLIAMS 2,592,501 l HYDRAULIC SCALE CAPSULE Filed Nov. 10, 1949 2 smETs--sfmm 1 mnentor APl'il 8 1952 L. s. WILLIAMS .2,592,591l

HYDRAULIC SCALE CAPSULE Filed NOV.. 10, 1949 2 Si-EETS-Sl-IET 2 Patented Apr. 8, 1952 HYDRAULIC SCALE CAPSULE Lawrence S. Williams, Toledo, Ohio, assignor to Toledo Scale Company, Toledo, Ohio, a corporation of New Jersey Application November 10, 1949, Serial No. 126,531

11 Claims. l

This invention relates to hydraulic weighing scales and in particular to improvements in the hydraulic load supporting elements commonly known as capsules.

In a hydraulic weighing scale the load receiver is supported by one or more hydraulic capsules that convert the load forces into corresponding hydraulic pressures. The hydraulic pressures are transmitted through pipes to pressure receivers, one for each capsule, that convert the hydraulic pressure into force which is balanced by suitable beam, spring or pendulum counterbalancing and indicating equipment. In order that such a scale be accurate it is necessary that the effective areas of the several capsules and pressure receiving units remain constant regardless of the magnitude of the loads being weighed and that the mechanical resistance to deformation of the capsules and pressure receiving units be reduced or eliminated so that variations in quantity of hydraulic fluid in the systems or elastic deformation of the pipes or other units cannot affect the accuracy of the force transmission through the hydraulic system. The construction of a capsule to satisfy these requirements requires painstaking care as to the materials and construction of the flexible portions of the capsule so that the capsule is both liquid tight and still mechanically free to convert all the load force to hydraulic pressure. The necessity for little or no mechanical resisting force, particularly in the capsules, may be easily understood when one considers the operation of a capsule as the quantity of fluid is varied. If the capsule is without mechanical resistance, the pressure of the hydraulic fluid within the capsule is the only force preventing the capsule from collapsing to a solid condition with its upper and lower plates in contact. If the effective area also remains constant with changes in fill then the pressure generated within the capsule is the same regardless of the quantity of hydraulic fluid. However, if the capsule has elastic resistance to deformation a portion of the hydraulic pressure is used to overcome the elastic resistance of the capsule whenever the quantity of fluid is increased so that the capsule exhibits too high a pressure for the given load. If the fill is decreased the elastic forces support a portion of the applied load and the hydraulic pressure is less than it should be.

It is furthermore highly desirable that the hydraulic capsules of a Weighing scale have considerable latitude in the acceptable quantities of fill so that temperature variations in the hydraulic fluid as well as compressibility of entrapped gas and elasticity of connecting pipes cannot, by varying the quantity of fill, introduce errors or differences vin pressure for given loads applied to the capsules.

The principal object of this invention is to provide an easily constructed hydraulic capsule that has very low mechanical resistance to deformation, that has a particularly constant effective area and that is capable of operating satisfactorily with widely different quantities of hydraulic fluid.

Another object of the invention is to provide a capsule in which one or more sheets of rubbery material are employed to line the interior of the capsule and retain the hydraulic fluid therein.

A still further object of the invention is to provide a simple structure for supporting the liner in the space between relatively movable parts of the capsule.

A still further object is to provide a simple structure for supporting the rubbery material which structure provides substantially constant effective area so that effective area of the capsule itself remains unchanged as the supported load varies. f

An ancilliary object of the invention is to provide a simple attachment for indicating the quantity of hydraulic fluid Within the capsule and the parallelism between the relatively movable portions of the capsule.

More specific objects and advantages are apparent from the following description of a preferred embodiment of the invention.

According to the invention the improved hydraulic capsule comprises first and second members that are held in spaced apart relation by hydraulic fluid contained within a bladder or between sealed together sheets of rubbery material interposed between the first and second members. One of the members includes a rim that surrounds the other of the members leaving a gap between the rim and the periphery of the other member. The bladder or rubbery sheet of material bulges into this gap and is supported therein by a plurality of sheets or strips of thin, non-stretchable, bendable material the ends of which are anchored to the rim and to the other member and the middle portions of which span, in generally semi-circular form, the gap between the rim and member to provide an annular basket or net to support the bladder or rubbery sheet. The thin, non-stretchable sheets or strips of material have lengths along the periphery of the gap sufficiently short so that each may lie in a cylindrical surface (a species of a surface having only one degree of curvature) and which may accommodate relative movement between the members by bending only without stretching of the material. If the capsule members are circular in outline the sheets or strips of material must be relatively narrow with each one occupying a very smalllength alongrthe periphery of the members. If the .capsule members are polygonal in form rather than circular each of the sheets or strips may have a length along the periphery substantially equal to the length of one of the sides of the polygon. 'Forease of machining the circular form is preferred.

The invention further contemplates that small lever-like indicators be includedon' oneof the members with an end of each lever resting on the other of the members so that theposition'ofv each lever is an indication of the separationrofv-the capsule members on that particular side'" of the 03951.41@ p ,lAfpreferred embodiment of the invention is illustrated in the accompanying drawings.

iFiguie I'is'an elevation/partly insection, of theXinrrlprovedcapsule,v a portion ofvthepedestal o 'which it'isgmounted, and a portion "of aA load iver supportedrby the capsule.

Ii'grllll is a'planview f aninverted capsule 'toi how the arrangement ofthe basemember an ;thesurrounding rim as well as theil'everlike indicators.

yE igure'l is an enlarged fragmentary vertical fseetion 'taken alongthe line III- Ill Of'Fi'gure Iljto'show K the1 cooperationof the capsule inem- -ber'rsg,the 'rubberyliner'and thevrim'- that is -atta'rhed to one? 'of'fthe membersy andthat surrounds fthe j other vof :the members.

r gure IV is-A another vertical fragmentary section/:taken along the line V-IV of vrFigure II to show one of the lever-like indicators and'its 'cbbperationfwith the capsule members.

lfFigure yV is an enlarged perspective View of afragmentiofthe liner and the strips of exible nnstrtchable material that support the' liner ifthe :gap between the relatively movable capsule members.

'fFigureVIis a perspective view of one of the kever--like-capsule height indicators.

f`Fi`g'ureVII-is a fragmentary sectional detail similar-to Fgure'fIII'fshowing a diierent'form of bladder or liner construction.

V'fliese specific'fgures and the accompanying 'description are intended merely to illustrate the invention butnot'to limit its scope.

j A 'hydraulic weighingl scale vcapsule constructed ."ccordrigto' theinvention comprises a pressure plate I jthat' is hydraulically supported from a baseinember 2l-which in turn rests on av cor- `ijugatedlead cushion 3 pla'cedpn Vtopv of'a pier The `pier may 4be formed as partr of the ,masonryjtvcrkin the pit housing the supporting j nismoftheweighing scale. yThe column base 'ssecuredby means of a plurality of bolts 6" tdtransmitload 'uniformly overA the greater p rtionfof,p'thepressure plateV I. A column l prifsingjthree cupped members 3, 9 'and-Ii! separatedbyperipherally grooved rubber inserts 'I'Ijis' erectedffrom :the column base` 5 and serves 'to'support an'girder 4I2 of a weighbridge or load l'ver that'is' supported in part by the'illus edfca'psule.y The peripherally grooved rubber,`jinserts II permit `lateral movement 'of the load i receiver without forcing corresponding jmoyenientsof the pressure plate I. as well vas .5,by a plurality of studs I6 carrying adjusting y nuts II and I8.

",Thepressure plate I is supported from the base 2 by hydraulicv fluid contained within a rubber 'sheets arel held in sealing relation by a .clamping rimf2I fthat surrounds the periphery of the base member 2 and that has an inwardly directed flange 22 underlying a radially extending ledge 2,3 of the base member 2. A plurality fof" -berdablefnon-stretchable strips -of material A2li lthat are anchord'- to vparallel `opposing faces '251and726 ofthe rim ZI-andtheledge 23 respectively, and that extend across--the gapbetween 'thesefacesfsupport the rubber liner sheet IS in the'gap while-permitting relative movement between-*the pressure Aplate I and base 2. The rimr 2I,5 which 'is' heldin place by a plurality of bolts" lspao'ed around -the periphery provides ajsim'ple r`structure'-for' supporting and sealing `the 'stripsl and the liners.

"*The'fsp'ace between thefliners land 2i), the space withinfthebladder, 'is in hydraulic comn jwith apressure receiver. For 'cone c incst'ructimi the upper bladder p01- tifcri'or liner 20' has a ,neck 28 "that is clamped in, nfopening leading through thepressure plate Ifand that is` 1in" direct.' communication with a disconnect `v'alve -29"xedly secured' to the end bf a'pipe 30 which .leadslto` thefpressure receiver..ofthe system. wThe disconnect valve 29 isfclampedbya' bolt'3l threaded',I through the top fof-a bridge 132 erectedfrom the pressure plate I" and 1 overlying "the opening from the bladdenneck 28. The disconnect valve 29v may be ofa separablev type that automatically closes the. end. of mthe tube` or. pipev 33 as well as the neck` of fthe bladderlitselfwhenever'it is released from `its clamped position.

Theplurality'offlever-likeindicators 33 each ofwhichis-supported-in a yokev34 attached to theunderside-ofvthe inwardly directed flange 22 r of the rimv 2I- has' an upturned -endy 35 bearing against alshoulder 36 of the base 2 andinas its other end'inf alignmentpwith a downwardly directeclnishedfsurface w3l of the exterior portion offthe rim2l. Y Acsspring 38" holds .the lever 33 in.-,aposition ,with .its Iupwardly "directed end -35 ibearingagainst theshoulder 36. If there is too much? hydraulic fluid'. in 'the .system the pressure .plate I .is- :raised withfrespect to' the base 2 and the endiofMthe indicator'` lever -33rises with respect to/Ithesuriace' 3l4 thus-indicating an..excessive ll. l.lil ewise`if' thell isn-insufficient Vthe press'urer'plate I dropsand' thelendi'ofv the lever 33 dropsycorrespondingly with respect to the surface 3I. f

A-yAlplurality offthese indicators (see Figure II) spaced 'at'intervals around the periphery of the capsule allow its condition of level to be ascertained as well as its condition of fill. "Its con- `pliti'ono'f'level is adjusted by means of the nuts VElfiYandi'-IBfthreaded on the studs I6. vLikewise the height of the capsule with respect to the load receiver or weigh beam girder I2 may be adjusted by screwing the threaded portion of the lower cupped column member 8 in or out of the column base to thus cause each of the several capsules carrying the load receiver to support its share of the load.

The nal leveling of the capsule should ordinarily be performed after the scale has been installed and loaded to its full capacity at least once. This loading to capacity is required to rmly set the base 2 on the corrugated lead cushion 3 which cushion yields in its highly stressed portions until the load is more or less uniformly distributed throughout the entire area of the base. This distribution of load is required to prevent failure of the capsule base 2 and to prevent further shifting of the capsules with applied loads. Since the lead cushion is non-resilient it permits the capsule to take its final position on the first loading to full capacity and to thereafter maintain that position without appreciable further change.

Referring now to Figure II the base 2 has a plurality of vertical radially directed ribs 39 connecting an annular central rib 40 and an outer circular rib 4|. This arrangement gives the maximum strength for a minimum quantity of metal in the casting forming the base 2. Likewise the rim 2| is cast with webs and recesses to provide maximum strength with minimum weight. Furthermore, this drawing of the base shows the four lever-like indicators 33 equally spaced around the periphery of the capsule.

Referring now to Figures III and V the periphery of the upper capsule liner 20 has an upturned rim 42 around its periphery which fit-s a corresponding groove cut in the pressure plate Likewise the rim 2| has a groove -which fits and receives a turned edge 43 of the lower liner 9. An upstanding rib 44 forming a side of the groove in the rim 2| is of such a height that when the liners |9 and 20 are in position with their turned edges 42 and 43 resting in the receiving grooves and the rim 2| is bolted tightly against the pressure plate the rib 44 squeezes the rubber liners to form a pressure tight seal. For convenience in assembly the turned edges 42 and 43 of the liners are made narrower and deeper than the corresponding grooves so that they may be easily slipped into place and then compressed to fill the grooves as the rim 2| is bolted into place. This construction makes it easy to assemble a capsule and to disassemble one for repair because none of the parts need be cemented or otherwise irremovably joined together in the assembly of the structure.

Referring to Figure V in particular, the supporting sheets .or narrow strips 24 that support against expansion in the bulging hemitoroidal bead 45 of the lower liner |9 are anchored, as by welding, to a pair of

bands

46 and 41. For convenience in construction the strips 24 are formed by laterally slitting a long strip cf material with the slits extending from one side of the long strip to the margin of the other side but not completely severing the strips from each other. The unsevered marginal area of the long strip is welded or otherwise secured throughout its length to the band 46. The strips 24 are then held in a mold or jig while their ends are welded to the other band 41. Because of the greater length of the band 41 the strips 24 are spaced apart slightly where they are attached to the band 41. This spacing apart however is not suiiicient to allow the rubber liner to protrude through the gaps between the strips.

It is pointed out that the

bands

46 and 41 are located outside the U-shaped form of the exible strips 24. The edges of these bands are made as nearly square as practical so that when they are assembled in the capsule the band 46 may t in a rabbet 48 in the periphery of the base 2 with its square edge supported against the shoulder of the rabbet. Likewise, the other band 41 fits into a rabbet 49 cut into the surface 25 of the rim 2|. The square edges of the bands and the sharp shoulders of the rabbets provide adequate support and anchorage for the bands and the bendable, non-stretchable strips 24 so that they may withstand the forces hydraulically exerted against the capsule liner I9.

Figures IV and VI illustrate in considerable detail the lever-like indicators 33 that are mounted from the yokes 34 with their upturned ends 35 bearing against the shoulders 36 of the base 2. As may be seen in Figure IV the lower surface of the end of the lever 33 is iiush with the lower surface 31 of the rim 2|. This is the normal adjusted position for the capsule.

In initial assembly a more exact ll is obtained through the use of stop screws 56 (Figure III) which are threaded through the inwardly directed flange 22 and contact the lower surface of the ledge of the base '2. Each of the screws 56 is of predetermined length and is threaded through a machined boss `5| of the flange 22. Their ends, resting against the machined surface of the ledge of the base 2, provide very definite positioning of the pressure plate with respect to the :base 2. The capsule is iilled to the limit permitted by the screws 5U and the lever-like indicators 33 are adjusted to the position shown in Figure IV. The stop screws 50 are removed during installation of the capsule in a scale to allow free movement of the capsule parts.

In normal operation of this hydraulic scale capsule the non-stretchable flexible strips 24 serving to support the bead 45 of the capsule liner I9 take a nearly semi-circular form between end portions which lie tangent to and against the surfaces 25 and 26 of the rim 2| and the base 2 respectively. If the pressure plate l and rim 2| move upwardly or downwardly with respect to the base 2 the strips 24 maintain their generally semi-circular form as they roll or unroll against the supporting surfaces.

The effective area of a capsule constructed according to the invention consists of the area of the base 2 plus half of the projected area of the gap between the base 2 and the rim 2|. The gap between the members must therefore be very accurately controlled so that the pressure exerted on the projected area of the gap and which is counteracted by tension in the strips 24 is properly divided between the rim 2| and the base 2. In the ideal capsule the strips 24 are non-stretchable membranes, i. e., they have no resistance to bending although they are non-stretchable. With membranes it may be shown mathematically that, at a distance from the center of the capsule equal to the radius of the effective area of the capsule, the strips are horizontal (their end portions resting against the rim 2| and capsule base 2 are vertical). In actual construction bendable nonstretchable thin metal strips are the closest possible approach to a true membrane and it is necessary that they approximate as closely as possible the shape assumed by a true membrane.

Furthermore to maintain a precisely predictl ciselydetermined. For this reason thestrips 2d are. arranged to .be 4supported directly in contact .with the accuratelyV machined surfaces of .the rim; and base rather .thanbeing supportedon intermediate constructional memberswhich in turn are supported against the rimand base. VThis eliminationof anymembers having appreciable tolerance in. dimensionserves to reduce the random errors. in eiiective area-between supposedly .identical capsules. VThe rubber -or rubber-like material-forming the Ycapsule linerlS need not Abezheld toA precisely constant dimensionsbecause it constitutes in effect a part of the hydraulic iiuid and `transmits the hydraulic force to the .strips-.24 without in itself affecting the force transmission.

Thecapsule liners I9 and 2U together constitute a bladder serving to hydraulically seal the Ispace between the` base 2 and the pressure plate I. YInthe preferred-embodiment shown in Figures I to V inclusive `the bladder is made in two partsthat are held sealed together by pressure exerted against the rims of the liner elements I9 and 2 0. This is the preferred. type of construction because of the ease with which the capsule may be assembled and later disassembled for ren pair if such is necessary. However, it is also practical, from a constructional point of view, to makefthecapsule.liner inthe form of a sealed bladderrl (Figure VII). which bladder-is supported bystrips 52Hthe ends of which are an- Y chored-to a base- 53 and a rim :5t of a pressure platet. The only difference in construction be- .tween Jthis second example and the first example is theiconstruction ofthe liner as a single bag or bladder-like ,element that is made liquid tight before installation in the capsule.

In the ii-rst` example the liners -I 9 and 2li, which together constitute the bladder, have their edges heldsealedby a pressure tight joint that permits completerdisassembly should such be found desirable. Another advantage ofthe rst type of construction is the ease with which the rubber sheetsforming the liners maybe molded.

In either example the advantages of `the invention are clearly obtainedbecause in each example the bladder provides a liquidtight envelope which in itself contributes nothing to the weighing of load and which may be, by the use ofaccurately machined bases and rims with interconnecting exible strips, held to a precisely determined shape thus securing extremely accurate proportionality vbetween the loads applied to the pressure plate and thehydraulic pressures developed in the capsule as a result of those loads.

Various modications may be made in the specie details of construction without departing from the spirit and scope of the invention or losing the advantages obtained by employing a bladder or separable rubber-like liner in a capsule fora hydraulic weighing scale.

I claim:

l. In a hydraulic capsule forming part of a hydraulic force transmitting system for a weighing scale, in combination, a first member, a second member, a rim on the rst member that surrounds the periphery ofthe second member, a plurality of laterally juxtaposed bendable,'non stretchable strips that arch across the gap between the rim and the periphery ofthe second member andV that are anchored to the rim and to the secondnmember, an impervious bladder jen closed-between the membersand supported by the mem-bers and the plurality of juxtaposed strips, and a fluid. coupling incommunication with the interior of the bladder.

. 2'.y In a hydraulic-capsule iorming part of a hydraulic force transmitting systemfor a weighing 'sca-le, in combination, a first member, a seoondmem-ber, a rimon the first member that surrounds the peripheryl of the second member, opposing faces of the rimand second member being spaced 4apart and generally perpendicular to load receiving surfaces of the-members a plurality of laterally juxtaposed bendable non-stretchable strips that are anchored to the rim and to the second member and that arch between the opposing. facesioi the rim and member with portions resting against the faces, an impervious bladder enclosedgbetween the load receiving surfaces of the rst and second members andr supported by the members and the pluralityyof strips, and a fluid coupling in communication with the interior o1" the bladder.

3 Inr a-hydraulic capsule forming part of a hydraulic forcegtransmitting system 'for a weighing scale,`in combination, a rst member, a sec- 0nd member, a rim1on the iirst member that surrounds the peripheryof the second member, the opposing .faces of the rim and second member being right cylindricalv and spaced apart, a pluralityfof closely spaced; strips that are anchored to the rim and to the secondfmember and that arch-f-between-.the rim and member with the ends of thel archedportions resting against the cylindricalqfaces, fand an Vimpervious bladder having a fitting fforiiuid communication with its interior enclosed ,between 1 said members and supported against expansion by the members and strips.

4. :In a hydrauliccapsule forming part of a hydraulicv force transmitting system for a Weighing scale,fin-. combination, a first member, a second member, arim on the-first member arranged to surround theperiphery of the second member leaving a gap therebetween, an impervious bladder of stretchable .material having a tting for fluid communicationwith its interior interposed between-the -rst and second member and extending into the gapbetween the rim and the .periphery'of the second member, and a plurality ofclosely spaced bladder retaining members that are attached to the rim and-to the second'member with the attached portions of the retaining members parallelto. each other and the intermediate portion1arched-across the gap, said retainingmembers being resilient and non-stretchableto support the bladder without mechanically restricting relative movement between the rst andsecondmembers.

5; In` a hydraulic capsule forming part of a hydraulic force transmittingsystem for a weighing. scale;in combination, a first member, a secondmember, a rim on the rst member arranged to surround theperiphery of the second member leaving a gapbetween the rim and the second member,v an impervious bladder interposed between the rst and second members, a fluid coupling in` communication with the interior of the bladder, and a plurality of sheets of bendable non-stretchable material that are laterally juxtaposed and that are anchored to the rim and to the second member with the sheets arching across the-gap to form a support for the bladder.

6. AInal hydraulic capsule forming part of a hydraulic force transmitting system for a weighingscale;-inAcombinatiom arlrst'member, a second member having a generally circular periphery, a rim on the first member that surrounds the generally circular periphery of the second member, spaced apart parallel opposed surface on the rim and the second member, each of the surfaces having a shallow step, an impervious bladder interposed between said members and having a hemitoroidal section extending into the gap between the rim and the second member, a duid coupling in communication with the interior of the bladder, and a support for the hemitoroidal section comprising a plurality of closely spaced strips and a pair of bands, the strips being secured to the bands and the bands fitting the stepped surfaces of the rim and second member.

7. In a hydraulic capsule forming part of a hydraulic force transmitting system for a weighing scale, in combination, a first member, a second member having a generally circular periphery, a rim on the first member that surrounds the second member, a rabbet on each of the opposed surfaces of the rim and second member, a circular band tted into each rabbet, a plurality of closely spaced strips of bendable non-stretchable material that have their ends secured to the bands and that lie in part against the opposed surfaces of the rim and second member, said strips arching across the gap between the rim and the second member, an impervious bladder interposed between the first and second members and supported in the gap between the members by said plurality of strips, and a fluid coupling in cornmunication with the interior of the bladder.

8. In a hydraulic capsule forming part of a hydraulic force transmitting system for a weighing scale, in combination, a first member, a second member having a generally circular periphery, a rim on the first member that surrounds the second member, a rabbet on each of the opposed surfaces of the rim and second member, a first band that fits one of the rabbets, a sheet of resilient bendable non-stretchable material that along one edge is attached to the band, said sheet having a plurality of cuts perpendicular to the edge secured to the band to .divide it into a plurality of connected strips, a second band that ts the other rabbet, said strips being individually attached to the second band, and an impervious bladder that includes a fluid coupling in communication with the interior of the bladder and that is interposed between the first and second member and supported in the gap between the members by the plurality of strips attached to the bands fitted in the rabbets.

9. In a hydraulic capsule forming part of a hydraulic force transmitting system for a weighing scale, in combination, a iirst member, a second member having a generally circular periphery, a rim on the first member that surrounds the periphery of the second member, said rim and said second member having opposed parallel surfaces, a plurality of strips anchored to the rim and the second member and arching therebetween, a bladder having a fluid coupling in communication with its interior interposed between the members and supported in the gap between the members by said plurality of strips, and an inwardly directed ange on the rim that projects over the margin of the second member to prevent separation of the members.

10. In a hydraulic capsule forming part of a hydraulic force transmitting system for a weighing scale, in combination, a first member, a second member, a rim on the first member that surrounds the periphery of the second member, means for retaining hydraulic fluid between said members, a iiuid coupling in communication with the interior of said means, and an indicator for indicating the axial spacing between said members, said indicator comprising a lever that is fulcrumed on one of said members, that has another portion resiliently urged against the other member and that has its end in alignment with a reference point of one of the members when the members are correctly spaced.

11. In a hydraulic capsule forming part of a hydraulic force transmitting system of a weighing scale, in combination, a first member, a second member, a rim on the first member that surrounds the second member, means for retaining hydraulic fluid between the members, and an indicator for indicating the extent of axial separation of the members, the indicator comprising a lever that is fulcrumed on the rim with one end resiliently urged against the second member and the other end in alignment with a reference point on the rim when the members are correctly spaced.

LAWRENCE S. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 325,926 Garsed Sept. 8, 1883 2,076,071 De Bolt -i Apr. 6, 1937